package hot100;

import java.util.ArrayList;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * @author aodre , QQ : 480029069
 * @date 2023/10/18 15:26
 */
public class Sing {


    public static void main(String[] args) {

        ArrayList<Integer> list = new ArrayList<>();

        list.add(1);
        list.add(2);
        list.add(null);
        list.add(3);

        System.out.println(list);
        System.out.println(list.size());
        TreeMap<Integer,Integer> map = new TreeMap<>();
        TreeSet<Integer> set = new TreeSet<>();

//        set.add();





    }

}
